diff --git a/joj3_config_generator/generator.py b/joj3_config_generator/generator.py
index 2edc98a..f4a389c 100644
--- a/joj3_config_generator/generator.py
+++ b/joj3_config_generator/generator.py
@@ -26,8 +26,8 @@ def convert_joj3_conf(repo_conf: repo.Config, task_conf: task.Config) -> result.
         name=task_conf.task.name,
         # exact folder difference specified by type
         log_path=str(JOJ3_LOG_PATH),
-        expire_unix_timestamp=int(task_conf.release.end_time.timestamp()),
-        effective_unix_timestamp=int(task_conf.release.begin_time.timestamp()),
+        expire_unix_timestamp=0,  # will be handled in the health check stage
+        effective_unix_timestamp=0,  # will be handled in the health check stage
         actor_csv_path=str(ACTOR_CSV_PATH),  # students.csv position
         max_total_score=(
             repo_conf.max_total_score
diff --git a/joj3_config_generator/models/task.py b/joj3_config_generator/models/task.py
index 450e7b6..ac0c149 100644
--- a/joj3_config_generator/models/task.py
+++ b/joj3_config_generator/models/task.py
@@ -211,6 +211,11 @@ class Release(BaseModel):
     )  # timestamp = 0, no begin time
 
 
+class SubmissionTime(BaseModel):
+    begin: Optional[datetime] = None
+    end: Optional[datetime] = None
+
+
 class Task(BaseModel):
     name: str = "unknown"
 
@@ -219,6 +224,7 @@ class Config(BaseModel):
     root: Path = Path(".")
     path: Path = Path("task.toml")
     task: Task = Task()  # Task name (e.g., hw3 ex5)
+    time: SubmissionTime = SubmissionTime()  # Valid time configuration
     release: Release = Release()  # Release configuration
     stages: List[Stage] = []  # list of stage configurations
     groups: Groups = Groups()
diff --git a/joj3_config_generator/transformers/repo.py b/joj3_config_generator/transformers/repo.py
index 2fde0ad..d9da48c 100644
--- a/joj3_config_generator/transformers/repo.py
+++ b/joj3_config_generator/transformers/repo.py
@@ -95,6 +95,10 @@ def get_teapot_check_args(repo_conf: repo.Config, task_conf: task.Config) -> Lis
             task_conf.groups if task_conf.groups.name else repo_conf.groups
         )
         res.extend(["--group-config", group_config])
+    if task_conf.time.begin:
+        res.extend(["--begin-time", task_conf.time.begin.isoformat()])
+    if task_conf.time.end:
+        res.extend(["--end-time", task_conf.time.end.isoformat()])
     return res
 
 
@@ -108,7 +112,8 @@ def get_health_check_stage(
             name="local",
             with_=result.ExecutorWith(
                 default=result.Cmd(
-                    cpu_limit=common.Time("10s"), clock_limit=common.Time("20s")
+                    cpu_limit=common.Time("10s"),
+                    clock_limit=common.Time("20s"),
                 ),
                 cases=[
                     result.OptionalCmd(